A simple choice

At election time, it occurs to voters that certain candidates are, to put it simply, simple. For most candidates and their staff, this is the desired payoff for years of hard work. A study that appeared in 1997 in the journal Nature explains why.

Politicians' Uniquely Simple Personalities was written by the psychologists Gian Vittorio Caprara and Claudio Barbaranelli, of the University of Rome, and Philip Zimbardo of Stanford University in California. The title is wonderfully evocative, but slightly misleading. Scientists try to make sense of a complicated phenomenon by boiling it down into a few numbers. Voters try to make sense of a politician by doing much the same thing. A savvy candidate takes advantage of this.

Even the simplest person has a uniquely complicated personality. Yet most of us manage to size up other people's personalities. We do it all the time, without great difficulty. Psychologists say that, for practical purposes, almost anyone's personality can be boiled down to a mere five aspects (in psychology lingo, "five factors"). Now, precisely defining those aspects can be tricky - psychologists quarrel over that all the time. But the important thing is that just five seems to be plenty. You don't need 10, or 20, or 20m. Just five.

Caprara, Barbaranelli and Zimbardo wondered whether people boil down their politicians slightly further. After all, it comes down to just two choices: either "yes, I will vote for this person" or "no, I won't".

They tested this idea with more than 2,000 Italian citizens, asking each of them to make judgments about some famous individuals: politicians Silvio Berlusconi and Romano Prodi, skiing hero Alberto Tomba, and television celebrity Pippo Baudo. The Italian citizens were also asked to make judgments about themselves.

The results of the study: when people judged their own personalities or those of TV stars or sports heroes, they boiled things down to five factors. But when they judged a politician, it came down to just two: how energetic is he or she, and how trustworthy? Later, the scientists repeated their investigation in the United States, with similar results.

For helping us understand how we understand politicians, Caprara, Barbaranelli and Zimbardo were awarded the 2003 Ig Nobel prize in the field of psychology. Zimbardo later told a reporter from his home state of California (where Arnold Schwarzenegger is the elected governor): "Politicians like to think of themselves as so complex, but the electorate thinks of them as simple."

The striving to seem simple helps explain the campaign behaviour even of apparently complex, hard-to-classify candidates, be they Clintons or Blairs. It explains why most other candidates, too, try to seem even simpler than they are. Of course, no explanation is wanted or needed for the occasional case where a candidate is simply a simpleton.

· Marc Abrahams is editor of the bimonthly magazine Annals of Improbable Research (www.improbable.com), and organiser of the Ig Nobel Prize